Unidentified 10,000km wave looming over Venus 'surprises' researchers

An enormous and ominous stationary object has been identified in Venus’ atmosphere. But Japanese geophysicists believe it can probably be explained away as gravity waves passing over a mountain range.

“I was just surprised by its size, shape and strangeness, that it stayed at almost the same location,” Makoto Taguchi of Rikkyo University, Tokyo, and lead author on a paper describing the find, told WIRED. “We have never seen such a structure in past observations.” A description of the region, published in Nature Geoscience today, goes some way in explaining Taguchi’s shock. The bow-shaped, illuminated area took up an area reaching 10,000km across the cloud tops. It remained in-situ, captured by JAXA’s Akatsuki spacecraft over a series of days in 2015, remaining in almost exactly the same location.

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Being a geophysical expert, and not a UFO hunter, Taguchi reigned that surprise in and set about comparing the anomaly with everything he knew about the planet’s topography. Venus’ upper atmosphere is always covered in a thick layer of cloud made up of sulphuric acid, which move at speeds of 100m/s. As a result, it is virtually impossible to visually study the planet’s surface. We do have data on that surface, however, captured by a radar altimeter onboard the Pioneer Venus Orbiter back in the 90s.

Similar examples of such an anomaly have been captured before, but only here on Earth, Taguchi says. “In the terrestrial atmosphere a similar wave structure is caused by a stream flowing over high mountains - we call it a 'mountain wave',” he explains. “The largest of such a wave has a length of 1,000 km, but its shape is not a bow. I don't know other examples found in the planets other than Earth.”

Taguchi and his colleagues concluded that the bizarre, bright area must be hotter than the surrounding atmosphere, and was therefore likely a result of a gravity wave created lower down in the atmosphere rising and passing over a mountain range. More research is needed to verify this hypothesis, however.

Brightness temperature of the Venus disk

Planet-C

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“We have to study atmospheric conditions when the bow, [or] stationary gravity waves appear or not,” Taguchi explains. “First of all we have to collect more data for statistical studies.” His team may look at UV images to see if it can uncover data on the deceleration of the winds, due to gravity waves breaking along the mountain range.

“Image data from IR1 and IR2 onboard Akatsuki and vertical temperature profiles obtained by a radio occultation technique will be used for a study on the conditions deep in the lower atmosphere.”

“Computer simulations are also important to justify a hypothesis raised from the observational results. Bows in various spatial scales and conditions in the lower atmosphere that can reproduce observed thermal structures will be studied by computer simulations with a realistic surface topography.”